The present invention relates generally to a novel method for preparing 2,2',4,4',6,6'-hexanitrostilbene (HNS), an important thermally stable explosive material which is also useful as a nucleant for promoting optimum trinitrotoluene-crystallization.
The discovery and an early synthesis for preparing HNS is disclosed in U.S. Pat. No. 3,505,413 to K. Shipp. That reference teaches adding 2,4,6-trinitrotoluene (TNT) dissolved in an appropriate solvent to a metal hypochlorite solution to form trinitrobenzychloride (TNBCl), which will then react with the metal hydroxide normally present in the hypochlorite solution to form HNS. The reaction can be controlled by drowning the reaction mixture with an acid such as HCl during the TNBCl transition stage to obtain TNBCl and then reacting the TNBCl with a metal hydroxide such as NaOH to form HNS.
This reference also discloses a method for preparing 2,2',4,4',6,6'-hexanitrobibenzyl (HNB), a starting material necessary in the instant process, which will be more fully explained below.
Unlike the Shipp process, the instant method for preparing HNS involves the reaction of HNB and a quinone in a suitable solvent. This type of reaction can best be described as dehydrogenation by a quinone and is discussed by H. O. House in Modern Synthetic Reaction, 2nd Edition, 1972, W. A. Benjamin, Menlo Park, California, pp 37-44. However, the instant process operates under conditions different from those set forth by House. For example, House states that operative solvents include xylene and orthodichlorobenzene. However, as will be seen below these solvents do not work in the instant method whereas other solvents not previously disclosed for this type synthesis work quite well. Also, the quinones previously found operative with this type synthesis were those containing chlorine or cyano and chlorine groups. However, it has been discovered that benzoquinone, naphthoquinone and others also work while anthraquinone does not.